Beta‐thalassemia is caused by mutations in the beta‐globin gene (HBB) that result in a decrease or absence of beta‐globin production.1 There are more than 250 identified beta‐thalassemia mutations. The type of mutation is the major determinant of the clinical phenotype and the hematologic findings. Majority of the HBB mutations are within the exons or at the splice junctions that result in an absence of beta‐globin production (β0‐thalassemia). Other mutations in the promoter region or the 5′ or 3′‐untranslated region (UTR), introns, and some splicing abnormalities result in a decrease in beta‐globin production with mild or silent phenotype (β+ or β++‐thalassemia). Beta‐thalassemia can also result from large gene deletions and mutations outside the HBB.
